A portable phone has various functions in addition to a telephone function. Examples of those functions include an electronic mail function of transmitting and receiving electronic mails, a game function of executing games according to game programs, a digital camera function, and a television function of receiving and displaying television broadcasts. Also, in order to improve operability, there are portable phones having a main operation unit which includes a display device such as a liquid crystal display, and a touch pad that is attached to a display face of the display device and receives user's contact operation.
JP-A-2010-165289 discloses a portable phone which can be communicably connected to an external display device such as a television receiver so as to enable enlarged display of predetermined display information from the portable phone on the external display device, and then a portable phone can be used as an input device such as a mouse. This portable phone includes a light source, a lens, and an image sensor, and can be moved in arbitrary directions on a working face of a desk or the like. The light source emits light from the inside of a casing of the portable phone toward the working face. The lens condenses the light reflected by the working face. The image sensor detects the condensed light. According to the result of the detection of the image sensor, the portable phone obtains a movement direction and movement distance of the portable phone, and outputs the movement direction and the movement distance to the external display device.
JP-A-2007-123962 discloses a portable phone having a wireless mouse function. This portable phone calculates a movement direction and movement distance of the portable phone based on a displacement between images acquired by a built-in camera unit, and transmits the movement direction and the movement distance to a personal computer through a short-distance wireless communication unit. The personal computer controls movement and display of a pointer displayed on a monitor unit, based on the movement direction and the movement distance received from the portable phone.